Using bos fbx Error: "no module named UMIO"
From the error message it seems that you are using the BOS FBX importer with Blender 2.77.

The newest version of this add-on (at the time of this post) relies on precompiled libraries for Python 3.4 (see scripts/addons/io_scene_bos_fbx/win64bit/python34/UMIO.pyd) but Blender 2.77 ships with Python 3.5, so it won't be able to find the UMIO module.

Name                          Version
--------------------------------------------------
Blender 2.76                  Python 3.4
Blender 2.77                  Python 3.5
Blender 2.78                  Python 3.5

BOS FBX Importer 2015-07-04   Python 3.4


You need to either keep around a copy of Blender 2.76 to use this add-on with or ask the author to provide a newer version for Python 3.5.